Structural characterization and α-glucosidase inhibitory activity of polysaccharides extracted from Chinese traditional medicine Huidouba

In this research, the crude polysaccharides were extracted from Chinese traditional medicine Huidouba and then isolated and purified by DEAE-52 cellulose and Sephadex G-100 chromatographic columns. The hypoglycemic activities of two fractions were determined by α-glucosidase inhibitory activity in vitro. The fraction HDBP-3A showed the best α-glucosidase inhibitory activity with an IC₅₀ of 0.0075 mg/mL, which was lower than the acarbose positive control (IC₅₀ of 0.092 mg/mL). The structural features of HDBP-3A was investigated by the high-performance gel permeation chromatography (HPGPC), gas chromatography(GC), UV spectroscopy, FT-IR, periodate oxidation and Smith degradation. The results demonstrated that the HDBP-3A with a molecular weight of 86,749 Da mainly composed of l-rhamnose, d-fucose, l-arabinose, d-xylose, d-mannose, d-glucose and d-galactose with the molar ratio of 2.33:1.58:1.00:1.37:4.86:4.00:7.30. The branches of HDBP-3A were composed of (1 → 4)-linked, (1 → 6)-linked, (1 → 2)-linked or (1 → 3)-linked. The IR spectrum implied that β-pyranoside linkage and α-configurations existed in HDBP-3A simultaneously.